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IC 9133 



Bureau of Mines Information Circular/1987 



Estimation of Remaining Lode Gold 
Endowment in Selected Mining 
Districts of Alaska 



By Gary E. Sherman 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9133 



Estimation of Remaining Lode Gold 
Endowment in Selected Mining 
Districts of Alaska 



By Gary E. Sherman 




UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 




Library of Congress Cataloging in Publication Data: 






Sherman, G. E. (Gary E.) 

Estimation of remaining lode gold endowment in selected mining 
districts of Alaska. 

(Information circular/United States Department of the Interior, Bureau of Mines; 9133) 

Bibliography: p. 16. 

Supt. of Does, no.: I 28.27: 9133. 

1. Gold ores-Alaska. I. Title. II. Series: Information circular (United States. Bureau of 
Mines); 9133. 



TN295.U4 [TN423.A7] 622 s [553.4T09798] 86-607928 



CONTENTS 

Page 

Abstract 1 

Introduction 2 

Past and present gold production 4 

Methodology 5 

Estimation of remaining endowment 6 

Chichagof District 7 

Fairbanks District 8 

Homer District 9 

Hope-Seward District 10 

Juneau District 11 

Ketchikan District 12 

Prince William Sound District 13 

Willow Creek District 14 

Discussion 15 

References 16 

Appendix A. — Raw production data for districts analyzed 17 

Appendix B. — Regression analysis results, by district 23 

ILLUSTRATIONS 

1. Location of Alaska mining districts 3 

2. Alaska lode gold production (1891-1965) 4 

Grade-tonnage curve: 

3. Chichagof District 7 

4. Fairbanks District 8 

5. Homer District 9 

6. Hope-Seward District 10 

7. Juneau District 11 

8. Ketchikan District 12 

9. Prince William Sound District 13 

10. Willow Creek District 14 

TABLES 

1. Lode gold production, by district . 4 

2. Summary of districts analyzed 6 

Remaining endowment estimates: 

3. Chichagof District 7 

4. Fairbanks District 8 

5. Homer District 9 

6. Hope-Seward District 10 

7. Juneau District 11 

8. Ketchikan District 12 

9. Prince William Sound District 13 

10. Willow Creek District 14 

11. Summary of remaining endowment 15 



ii 

TABLES — Continued 

Page 

Raw production data: 

A-l. Chichagof District 17 

A-2. Fairbanks District 18 

A-3. Homer District 18 

A-4. Hope-Seward District 19 

A-5. Juneau District 20 

A-6. Ketchikan District 21 

A-7. Prince William Sound District 22 

A-8. Willow Creek District 22 





UNIT OF MEASURE ABBREVIATIONS USED 


IN THIS REPORT 


pet 


percent tr oz 


troy ounce 


St 


short ton tr oz/st 


troy ounce per short ton 


st/d 


short ton per day yr 


year 



ESTIMATION OF REMAINING LODE GOLD ENDOWMENT 
IN SELECTED MINING DISTRICTS OF ALASKA 



By Gary E. Sherman 1 



ABSTRACT 

The Bureau of Mines estimated the remaining lode gold endowment of 
eight mining districts in Alaska using historic production data. A log- 
arithmic model of cumulative tonnage of ore processed versus cumulative 
grade was applied to the following districts: Chichagof, Fairbanks, 
Homer, Hope-Seward, Juneau, Ketchikan, Prince William Sound, and Willow 
Creek. 

To assess the remaining endowment, a computerized production data base 
was compiled from Bureau records. These data were aggregated in 5-yr 
intervals for each district. Data were sorted in order of declining 
grade, and log cumulative grade was plotted against log cumulative ton- 
nage. Linear regression was performed on the data for each district. 
The linear equation for each curve was used to predict remaining endow- 
ment at a limiting mining grade. 

Based on conservative extrapolation of the grade-tonnage curves, a 
substantial total endowment of 8,415,100 tr oz of gold remains in the 
eight districts. The districts with the greatest remaining endowment 
are the Juneau, Chichagof, Fairbanks, and Willow Creek Districts. 

1 Physical scientist, Alaska Field Operations Center, Bureau of Mines, Juneau, AK. 



INTRODUCTION 



The Bureau of Mines Minerals Availabil- 
ity Program (MAP) was established in 1974 
to systematically assess mineral supplies 
from domestic and foreign sources. In 
the context of MAP goals, an assessment 
of the remaining lode gold endowment for 
eight mining districts in Alaska was 
undertaken. 

Exploration activity in Alaska has de- 
clined dramatically in recent years, ow- 
ing primarily to metal price declines; 
however, there has been a renewed inter- 
est in the potential of past lode gold 
producers. Many past producing lode gold 
mines in Alaska were unable to resume 
production owing to economic conditions 
following World War II. Others discon- 
tinued production owing to declining 
grade or the lack of adequate reserves. 
Many of the past producers in Alaska may 
contain significant remaining resources 
of gold. 

Several studies have used grade- 
tonnage relationships in examining the 
characteristics of ore deposit types and 
metal contents (J_"_3)« 2 Lasky (4) estab- 
lished what has become known as Lasky 's 
law, in which cumulative log tonnage 
plotted against cumulative grade exhibits 
a linear relationship for many deposit 
types. This is a negative exponential 
relationship of the form g = C1-C2 log t, 
where g is average grade, t is tons, and 
C] and C2 are constants. Lasky suggested 
that the tonnage-grade distribution for 
porphyry copper deposits could be used to 
estimate unknown copper resources by ex- 
trapolating the curve to some limiting 
cutoff grade (_5). 

Cargill (JO used historic production 
data to predict remaining usable re- 
sources in a log grade-log tonnage model. 
Use of historic production data inher- 
ently includes geologic, economic, and 
political conditions that have influenced 
production. The preferred method would 
be to measure cumulative return per unit 
effort, where effort includes such 

2 Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding the appendixes at the end of 
this report. 



factors as exploration, extraction, pro- 
cessing, and transportation (_6)» Since 
data on effort are generally lacking in 
the mineral industry, cumulative average 
grade is used in its place. Cargill ex- 
plained the method as follows: 

The underlying premise of this pro- 
duction-grade method of estimating 
usable resources is that the sum of 
industry experiences is reflected in 
its production and discovery statis- 
tics. This premise is true because 
the mineral and petroleum industries 
continuously adjust to economic and 
technologic pressures (each industry 
is forced by free market economics 
toward the lowest cost product), as 
well as to increasing geologic 
knowledge. .. .The suggestion that the 
future course of a mining industry 
can be estimated from its production 
history dates back at least to 1929 
(D.F. Hewett). 

Production data were grouped in 5-yr 
intervals by Cargill to minimize yearly 
variations in the data, and a least- 
squares fit to the line was made using 
the equation 

log y = bo + [bi log x], (1) 
where y = cumulative average grade, 

x = cumulative ore, 

bo = a constant, 

and bi = slope of the line. 

Regression was performed to minimize the 
expression 

n 

I (log y, - b - [b, log x,]) 2 > (2) 
i=l 

where n = number of data points, 

yj, = cumulative grade, ith period, 

and x | = cumulative ore, ith period. 



Cargill (_7) proved that, for any point 
on the curve, 



y = L /(l+b,), 
where Lq = limiting grade. 



(3) 



By selecting an average mining grade 
and using equation 3 to determine cumula- 
tive grade, the initial tonnage of ore at 
the mining grade can be estimated. Sub- 
traction of past production yields the 
usable resources available at the mining 
grade chosen. 

Harris (8) expressed concern about the 
method used by Cargill. He suggested 
that a reordering of the data by declin- 
ing grade may be appropriate in certain 
cases. Such a reordering can produce a 
curve that is more linear than one based 
on a time series. Harris argued that by 
equating cumulative grade with cumulative 
effort, bias can be introduced when, for 



example, economic conditions force high 
grading of an ore body. This upsets the 
orderly decline of cumulative grade with 
time. However, Harris stated that reor- 
dering of production data may not be 
strongly indicated when there has been a 
significant decrease in grades over the 
life of a mine and when a grade-tonnage 
relation is fitted only to the low-grade 
portion of the data. Under these circum- 
stances, the influence of grade varia- 
tions in early years at relatively high 
grades is of little consequence. This is 
true because the cumulative average for 
the low-grade portion of the data may be 
unaffected by reordering production data 
at the earlier high grades (8_). 

Historically, grade-tonnage relation- 
ships provide an estimate of the physical 
stock or endowment (8^). Use of the 
reordered production data results in 
modeling of the physical stock, not a 
quantity-effort relationship as used by 



Barrow, 



*■ 



y 



Ancho 



airbank s 




,Kodi«k 



. ■•' 









Mining Districts 

1 Chichagof 

2 Fairbanks 

3 Homer 

4 Hope - Seward 

5 Juneau 

6 Ketchikan 

7 Prince William Sound 

8 Willow Creek 



300 
I 



Scale, miles 




FIGURE 1.— Location of Alaska mining districts. (Modified from Ransome and Kerns (9).) 



Cargill (6^, since production is ordered 
by declining grade and not by year. 

Based on Harris 1 arguments, it was de- 
cided that reordering of the data by de- 
clining grade was the best approach for 
this study. Cumulative log grade-log 
tonnage curves were constructed for each 
district to provide an estimate of the 
nonproduced portion of the lode gold 



endowment. Production data from the 
Chichagof , Fairbanks, Homer, Hope-Seward, 
Juneau, Ketchikan, Prince William Sound, 
and Willow Creek Districts were analyzed. 
Locations of the districts examined are 
shown in figure 1. Mining district names 
and boundaries follow the convention of 
Ransome (9). 



PAST AND PRESENT GOLD PRODUCTION 



TABLE 1. - Lode gold production, by 
district ' 

(Ranked in descending order) 



District 

Juneau 

Chichagof 

Willow Creek 

Fairbanks 

Prince William Sound. 

Chistochina 

Alaska Peninsula 

Ketchikan 

McGrath 

Unclassified 2 

Homer 

Hope 

Kantishna 

Nome 

Petersburg 

Admiralty 

Anchorage 

Seward 

Iditarod 

Bonnifield 

Hyder 

Valdez Creek 

Nizina 

Innoko 

Chisana 

Kodiak 

Fairhaven 

Chandalar 

Aniak 

Yentna 

Redoubt 

Total 



Gold, tr oz 

5,652,776.00 

826,739.00 

611,833.20 

233,347.10 

137,889.60 

56,843.55 

51,692.54 

51,305.35 

38,592.88 

17,213.60 

16,026.58 

15,113.53 

7,643.59 

6,189.17 

5,913.23 

4,997.13 

4,478.78 

3,020.15 

2,892.06 

2,301.27 

2,240.57 

1,700.80 

1,363.26 

478.91 

172.00 

71.24 

70.19 

70.00 

49.70 

1.65 

.24 

7,753,026.87 



Districts with Bureau production re- 
cords. 

Production for which no district could 
be assigned owing to lack of information. 



Total gold production from Alaska 
(1880-1984) has been estimated at 31 mil- 
lion tr oz-(lO). Available Bureau data 
for the period 1891 to 1965 indicate a 
total lode production of 7,753,027 tr oz. 
Table 1 summarizes actual lode gold pro- 
duction by district, sorted in descending 
order. The majority of lode gold produc- 
tion in Alaska came from the Alaska Ju- 
neau Mine and the Treadwell group (the 
Treadwell, Mexican, Ready Bullion, and 
700 Foot Mines), both in the Juneau Dis- 
trict. As seen in figure 2, lode gold 
production dropped sharply after 1917 ow- 
ing to the cave-in and subsequent closure 
of the Treadwell group, and again in 1942 
following the issuance of War Production 
Board order L-208, which declared gold 
mining a nonessential wartime industry. 
Economic conditions following World War 
II prevented the resurgence of major lode 
mining activity, even though attempts 
were made to open mines with known 



320 




1891 



1901 



1921 



1931 



1941 



1951 



1961 



1971 



FIGURE 2.— Alaska lode gold production (1891-1965). Miss- 
ing portions of the curve indicate lack of data. Based on 
Bureau of Mines production data. 



reserves. Lode gold production in recent 
years has been limited to small-scale 
(less than 200-st/d) operations such as 
the Little Squaw Mine in the Chandalar 
District, the Independence Mine in the 



Willow Creek District, and the Grant Mine 
in the Fairbanks District. 

Gold production in Alaska in 1984 ex- 
ceeded 175,000 tr oz , virtually all of it 
from placer deposits (10). 



METHODOLOGY 



Alaskan lode gold production records 
compiled by the Bureau from 1891 through 
1965 were entered into a computerized 
data base to allow retrieval and manipu- 
lation. The production records are a 
combination of mint, smelter, and Bureau 
canvass records. These data are often 
lacking in terms of total production for 
a given mine, but were considered com- 
plete enough to attempt an estimation of 
remaining gold endowment. 

The eight districts for analysis were 
chosen based first on the quantity of in- 
formation available and secondly on the 
completeness of the historic production 
data. Many of the individual mine rec- 
ords lack key information such as tons 
of ore processed per year and mine name. 
In some cases only yearly district or re- 
gional totals were available. 

Where information allowed, missing an- 
nual tonnages were estimated. This was 
accomplished by using an average grade of 
production for a block of years surround- 
ing the year with no tonnage data. Only 
years with comparable production levels 
(troy ounces) were used to compute the 
average grade. The tonnage was then es- 
timated by dividing the troy ounces pro- 
duced in the missing year by the average 
grade for the block of surrounding 
years. 

When no annual tonnage figures were 
available for most of the district, the 
data could not be used in the model. 
Other districts are dominated by mines 
that produced gold from primary copper 
deposits. These deposits have lower gold 
grades than epithermal gold deposits and 
cannot be aggregated without changing the 
nature of the grade-tonnage relationship. 
Aggregating data across deposit types may 
introduce a high degree of variability in 
the grade-tonnage curve; therefore data 
were restricted to production from pri- 
mary lode gold (quartz vein) deposits. 
An exception to this is the treatment of 



the Juneau District, in which production 
was dominated by large low-grade deposits 
(Alaska Juneau and Treadwell Mines). 
Data for the quartz vein deposits were 
aggregated with those for the low-grade 
deposits. Since the "high-grade" quartz 
vein deposits accounted for less than 
10 pet of the production from the dis- 
trict, these data exert little influence 
on the cumulative curve. 

Production records were cross refer- 
enced with the Bureau of Mines Minerals 
Availability System (MAS) sequence number 
for each deposit to verify that each mine 
was assigned to the proper district. 
Following elimination of duplicate and/or 
secondary records, the data were aggre- 
gated in 5-yr intervals for each dis- 
trict. Cumulating the data over a 5-yr 
period smooths the cumulative grade- 
tonnage curve by lessening the yearly 
variation. Curves were plotted, and a 
least-squares regression analysis was 
performed to fit a linear equation to 
each line. Extrapolation of the curve to 
a limiting grade provided an estimate of 
remaining gold endowment. Remaining en- 
dowment is defined for the purpose of 
this study as the nonproduced portion of 
the mineralized rock (at a limiting 
grade) associated with lode gold deposits 
that have produced in the past. Limiting 
grade is chosen to be less than the low- 
est production grade in the district, but 
greater than a technologic cutoff grade. 
Vein gold deposits in Alaska generally 
had a production grade greater than 
0.2 tr oz/st. The Juneau District depos- 
its produced at grades of less than 
0.15 tr oz/st. Based on these historical 
values, the limiting grade (grade at 
which remaining endowment was calculated) 
was taken to be 0.1 to 0.2 tr oz/st less 
than the historic production grades. 
Care should be taken not to extrapolate 
the curves beyond reasonable limit. 
Taking a very low limiting grade can 



result in estimates that are astronomi- 
cally high and probably invalid. 

Most of the cumulative grade-tonnage 
curves for the districts examined illus- 
trate an upper high-grade portion with a 
flatter slope than the rest of the curve. 
This is because many of the mines in 
Alaska were short-lived, high-grading op- 
erations. For a mine (and therefore ag- 
gregated district data) to exhibit an or- 
derly decline in grade over time, the 
mining operation must operate over a suf- 
ficient time span to allow a representa- 
tive sampling of the ore body. Because 
of this, the upper data points were 
dropped in the regression analyses for 
all of the districts except Chichagof, 
Juneau, and Willow Creek. 



The estimate of remaining endowment is 
based on an average limiting grade. Lim- 
iting grade is converted to a cumulative 
grade using equation 3. This cumulative 
grade is used in the equation 



= io(( lo g y 



b )/b,). 



(4) 



The tonnage x represents the total amount 
of ore originally present at cumulative 
grade y. Total gold present is equal to 
the product of x and y. Subtracting the 
previous production from the original 
amount of gold present yields an estimate 
of remaining endowment in troy ounces of 
gold. 



ESTIMATION OF REMAINING ENDOWMENT 



Table 2 shows the eight districts 
chosen for analysis along with the number 
of mines in the data set, documented pro- 
duction, total tons of ore produced, and 
average grade. Documented production is 
defined as gold production for which an- 
nual tons of ore produced are known. 
Tonnage of ore per year is essential in 
forming the cumulative grade-tonnage 
curve; mines lacking this information are 
not included in the analysis. For this 
reason, the production figures for each 
district in table 2 are less than those 
in table 1. 

Individual estimates by district are 
discussed in the following sections. For 



each district a table lists the remaining 
gold endowment estimates for a range of 
limiting grades. The range of estimates 
is given for each district to illustrate 
the dependency of the estimate on the 
limiting grade chosen. As stated pre- 
viously, at some point the limiting grade 
becomes meaningless in terms of mining, 
and the endowment estimate can approach 
astronomical proportions. 

A total remaining gold endowment of 
8,415,100 tr oz was estimated for the 
eight districts. Appendix A presents raw 
production data for the eight districts, 
and appendix B gives regression analysis 
results by district. 



TABLE 2. - Summary of districts analyzed 



District 



Number of 
mines 



Documented 
production, 
tr oz gold 



Total 
ore, st 



Average 

grade 
tr oz/st 



Chichagof 

Fairbanks 

Homer 

Hope-Seward 

Juneau 

Ketchikan 

Prince William Sound. 
Willow Creek 



56 
8 
20 
28 
37 
27 
28 



787,347 
230,499 
10,391 
17,587 
5,583,121 
16,042 
82,777 
607,726 



827,313 

195,071 

9,020 

18,271 

116,089,758 

38,175 

74,818 

539,624 



0.95 

1.18 

1.15 

.96 

.05 

.42 

1.11 

1.13 



dumber of mines included in the analysis. 



TABLE 3. - Remaining endowment estimates, 
Chichagof District 



Limiting 

grade, 
tr oz/st 


Cumulative 

grade, 

tr oz/st 


Original ore 
available, st 


Remaining gold 

endowment , 

tr oz 


0.1 


0.183 

.366 

.549 

.732 

.915 

1.097 

1.280 

1.463 


32,386,600 

7,019,100 

2,869,600 

1,521,200 

929,800 

623,200 

443,400 

330,200 


5,139,400 


.2 

.3 

.4 


1,781,600 

788,100 

1 326,200 


.5 

.6 


63,400 



.7 











Estimate of remaining endowment based on historic grades. 



CHICHAGOF DISTRICT 

Production from the Chichagof District 
(table 3) came primarily from the Hirst- 
Chichagof and the Chichagoff Mines. 
These two mines accounted for over 98 pet 
of the gold produced in the district. 
Figure 3 is a plot of the cumulative 
grade-tonnage data. Linear regression of 
the data in figure 3 yields values of 
2.67 for bo and -0.453 for bi. The low- 
est grade material produced in the 
Chichagof District was ore with a grade 
of 0.49 oz/ton. Using 0.4 oz/ton as a 
limiting grade in equation 4, the esti- 
mated remaining endowment of gold in the 
district is 326,200 tr oz. Since the 
majority of the production data came from 
two mines and continued over a signifi- 
cant time span, the grade-tonnage curve 
fits the model well. Table 3 shows 



estimates of remaining endowment for the 
Chichagof District over a range of limit- 
ing grades. 




LOG 



5\4 

CUMULAT 



FIGURE 3.— Grade-tonnage curve, Chichagof District. 



TABLE 4. - Remaining endowment estimates, 
Fairbanks District 



Limiting 

grade, 
tr oz/st 



Cumulative 

grade, 

tr oz/st 



Original ore 
available, st 



Remaining gold 

endowment , 

tr oz 



0.1. 
.2. 
.3. 
.4. 
.5. 
.6. 
.7. 



0.123 
.246 
.369 
.491 
.614 
.737 
.860 
.983 



42,718,665,800 

1,028,435,000 

116,265,200 

25,031,500 

7,525,100 

2,819,500 

1,229,700 

599,300 



5,254,165,400 

252,764,500 

42,671,400 

12,060,000 

4,389,900 

1,847,500 

1 827, 000 

358,600 



Estimate of remaining endowment based on historic grades. 



FAIRBANKS DISTRICT 

Gold production in the Fairbanks Dis- 
trict came from a number of mines, many 
with a short production span. The 
Clearly Hill, Free Gold, Hi Yu , and 
McCarty Mines accounted for 65 pet of the 
district production. 

Figure 4 shows the cumulative grade- 
tonnage curve for the district. The 
upper data point was eliminated from the 
data set for the purposes of the regres- 
sion since it represents a small high- 
grade portion of the total district pro- 
duction. Regression yielded an equation 
with values of 1.07 for bo and -0.186 for 
b]. Based on the aggregated data, a 
grade of 0.895 tr oz/st was the lowest 
average grade mined in the district. 
Using a limiting grade of 0.7 tr oz/st, 
a total remaining endowment of 827,000 
tr oz gold was estimated for the 



Fairbanks District. Table 4 shows the 
estimates for the district over a range 
of limiting grades. 




45 4.7 

LOG CUMULATIVE 



A3 5.1 

TONNAGE, 



FIGURE 4.— Grade-tonnage curve, Fairbanks District. 



TABLE 5. - Remaining endowment estimates, 
Homer District 



Limiting 

grade, 
tr oz/st 


Cumulative 

grade, 
tr oz/st 


Original ore 
available, st 


Remaining gold 

endowment, 

tr oz 


0.1 


0.127 
.255 
.382 
.509 
.637 
.764 
.892 

1.019 


246,486,300 

9,617,500 

1,466,500 

385,700 

135,800 

58,300 

28,300 

15,300 


31,293,400 


.2 


2,442,100 


.3 

.4 

.5 

.6 


549,800 

185,900 

76,100 

34,200 


.7 


14,900 


.8 


'5,200 



Estimate of remaining endowment based on historic grades. 



HOMER DISTRICT 

Gold production in the Homer District 
came primarily from the Nuka Bay region 
and is based on data from eight mines 
which produced high-grade ore over a 
20-yr period. Figure 5 is the cumulative 
grade-tonnage curve for the district. 
The upper data point was eliminated from 
the data set in the regression analysis. 
Regression of the curve yielded coeffi- 
cients of 0.91 for b and -0.215 for b,. 
Past mining reached a lower grade of 
0.94 tr oz/st. Using a limiting grade of 
0.8 tr oz/st yields an endowment estimate 
of 5,200 tr oz of gold. Table 5 shows 
the remaining endowment estimates for the 
district over a range of limiting grades. 




.07 - 



3.2 3.4 

LOG CUMULAT 



3.6 3.8 

TONNAGE, 



FIGURE 5.— Grade-tonnage curve, Homer District. 



10 



TABLE 6. - Remaining endowment estimates, 
Hope-Seward District 



Limiting 

grade, 
tr oz/st 



0.1. 
.2. 
.3. 

.4. 
.5. 
.6. 
.7. 



Cumulative 

grade, 

tr oz/st 



0.131 
.263 
.394 
.525 
.656 
.788 
.919 

1.050 



Original ore 
available, st 



88,300,700 

4,734,200 

867,600 

260,000 

102,000 

47,300 

24,800 

14,200 



Remaining gold 
endowment, 
tr oz 



11,549,800 

1,227,500 

324,200 

1 118,900 

49,300 

19,700 

5,200 





Estimate of remaining endowment based on historic grades. 



HOPE-SEWARD DISTRICT 

Data for the Hope and Seward Districts 
were combined to produce the cumulative 
grade-tonnage curve in figure 6. All 
mines in the district occur in the Valdez 
Group of metasediments and are typically 
small, high-grade vein deposits (11). 
Many of the mines produced over a 10-yr 
period. The most sustained production 
came from the Lucky Strike Mine, which 
was active for 26 yrs. 

The upper data point on the grade- 
tonnage curve was eliminated from the 
data set in the regression analysis. Re- 
gression yielded coefficients of 1.01 for 
bo and -0.238 for bj. The lowest grade 
mined previously in the district was 
0.54 tr oz/st; using a limiting grade of 
0.4 tr oz/st, an estimated 118,900 tr oz 
of gold remain. Table 6 shows remaining 



endowment estimates 
limiting grades. 



over a range of 




FIGURE 6.— Grade-tonnage curve, Hope-Seward District. 



TABLE 7. - Remaining endowment estimates, 
Juneau District 



11 



Limiting 

grade, 
tr oz/st 



0.01. 
.02. 
.03. 
.04. 
.05. 
.06. 
.07. 
.08. 



Cumulative 

grade, 

tr oz/st 



0.016 
.032 
.047 
.063 
.0883 
.1060 
.1237 
.1413 



Original ore 
available, st 



2,572,130,300 

385,683,100 

134,652,600 

60,379,700 

32,496,300 

19,614,200 

13,130,400 

9,053,800 



Remaining gold 

endowment, 

tr oz 



35,571,000 
'6, 758, 700 
745,600 








Estimate of remaining endowment based on historic grades. 



JUNEAU DISTRICT 

The Alaska Juneau and Treadwell group 
mines accounted for 91 pet of the gold 
production in the Juneau District. Fig- 
ure 7 is a cumulative grade-tonnage plot 
for the district. The more gently slop- 
ing upper part of the curve is due to the 
large influence of relatively higher 
grade material from the Treadwell group. 
According to Bureau records, the grades 
at the Treadwell and Alaska Juneau mines 
averaged 0.11 and 0.03 tr oz/st respec- 
tively. Based on Bureau data used in the 
grade-tonnage model, the Treadwell group 
processed over 19 million tons of ore, 
thus influencing the grade-tonnage curve 
to a large extent. 

To include the influence of the Tread- 
well group production in the endowment 
estimate, all data points were used in 
the regression analysis. The resulting 
least-squares fit is not as good as could 
be obtained by eliminating the upper two 
points; however, including the Treadwell 
data yields a more realistic estimate of 
the remaining gold endowment in the Ju- 
neau District. 



The resulting regression equation has 
coefficients of 2.14 for bo and -0.428 
for b]. At a limiting mining grade of 
0.02 tr oz/st, 6,758,700 tr oz of gold 
remain as predicted by the grade-tonnage 
model. Table 7 lists the remaining gold 
endowment estimates over a range of lim- 
iting grades. 




LOG CUMULATIVE TONNAGE, st 

FIGURE 7.— Grade-tonnage curve, Juneau District. 



12 



TABLE 8. - Remaining endowment estimates, 
Ketchikan District 



Limiting 

grade, 
tr oz/st 


Cumulative 

grade, 

tr oz/st 


Original ore 
available, st 


Remaining gold 

endowment, 

tr oz 


0. 1 


0.158 
.317 
.475 
.634 
.792 
.950 
1.109 
1.267 


527,900 

79,800 

26,600 

12,200 

6,700 

4,100 

2,700 

1,900 


67,400 


.2 


1 9,300 


.3 

.4 






.5 





.6 





.7 

.8 











Estimate of remaining endowment based on historic grades. 



KETCHIKAN DISTRICT 

Gold produced from the Ketchikan Dis- 
trict came from deposits with markedly 
lower grades than the other districts, 
except for the Juneau District. Most of 
the gold in the district was produced as 
a byproduct from primary copper mines. 
Only production data from primary lode 
gold deposits are included in the estima- 
tion of remaining gold endowment. Aver- 
age grade of the deposits in the data set 
was 0.42 tr oz/st, compared with grades 
near or above 1.0 tr oz/st in the other 
districts (excluding Juneau). 

Figure 8 is the cumulative grade- 
tonnage curve on which the regression was 
performed. The upper two data points 
were eliminated from the data set in the 
regression. Regression yielded coeffi- 
cients of 1.31 for bo and -0.369 for bj. 
Based on the lowest mined grade of 
0.28 tr oz/st, a limiting grade of 



0.2 tr oz/st was used to estimate the 
remaining gold endowment. This yielded a 
total of 9,300 tr oz of gold. Table 8 
shows the remaining endowment over a 
range of limiting grades. 




o -.4 

O 2.8 



3 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 
LOG CUMULATIVE TONNAGE, st 



FIGURE 8.— Grade-tonnage curve, Ketchikan District. 



TABLE 9. - Remaining endowment estimates, 
Prince William Sound District 



13 



Limiting 

grade, 
tr oz/st 


Cumulative 

grade, 

tr oz/st 


Original ore 
available, st 


Remaining gold 

endowment , 

tr oz 


0.1 


0.183 

.367 

.550 

.733 

.917 

1.100 

1.283 

1.467 


3,926,000 

849,200 

348,700 

185,300 

113,200 

75,900 

54,100 

40,300 


635,700 


.2 

.3 


228,900 
109,000 


.4 


1 53,000 


.5 


21,000 


.6 

.7 


700 






Estimate of remaining endowment based on historic grades. 



PRINCE WILLIAM SOUND DISTRICT 



The Prince William Sound District pro- 
duced 82,777 tr oz of gold from rela- 
tively high-grade quartz vein deposits. 
The largest producers were the Cliff and 
Granite Mines. Figure 9 shows the cumu- 
lative grade-tonnage curve for the dis- 
trict. The upper data point was elim- 
inated from the data set for purposes of 
the regression. Regression yielded coef- 
ficients of 2.26 for bo and -0.455 for 
bi« Based on 0.44 tr oz/st as the lowest 
grade mined, a limiting grade of 0.4 was 
used in the regression equation to pre- 
dict remaining endowment. A total of 
53,000 tr oz of gold are estimated to re- 
main in the district. Table 9 lists re- 
maining endowment estimates over a range 
of limiting grades. 




LOG CUMULATIVE TONNAGE, st 



FIGURE 9.— Grade-tonnage curve, Prince William Sound 
District. 



14 



TABLE 10. - Remaining endowment estimates, 
Willow Creek District 



Limiting 

grade, 
tr oz/st 



0.1. 
.2. 
.3. 
.4. 
.5. 
.6. 
.7. 



Cumulative 

grade, 

tr oz/st 



0.127 
.254 
.381 
.508 
.635 
.763 
.890 

1.017 



Original ore 
available, st 



15,722,138,900 

608,907,100 

90,909,000 

23,582,500 

8,280,200 

3,499,200 

1,699,600 

909,100 



Remaining gold 

endowment , 

tr oz 



1,996,103,900 

154,054,700 

34,028,600 

11,372,200 

4,650,200 

2,062,200 

904,900 

'316,800 



Estimate of remaining endowment based on historic grades. 



WILLOW CREEK DISTRICT 



The Willow Creek. District was the third 
largest producer of gold in Alaska. The 
majority of production came from the In- 
dependence, Fern, Lucky Shot, War Baby, 
and Gold Cord Mines. Exploration, devel- 
opment, and minor production have taken 
place in the district in the last 5 yr. 

Figure 10 shows the cumulative grade- 
tonnage curve for the district. Regres- 
sion of the data yielded coefficients of 
1.28 for bo and -0.213 for by. Based on 
0.87 tr oz/st as the lowest grade pro- 
duced in the district, an estimated 
316,800 tr oz of gold remain at a limit- 
ing grade of 0.8 tr oz/st. Table 10 
shows the remaining endowment estimates 
over a range of limiting grades. 




5.1 53 

CUMULATIVE 



55 5.7 

TONNAGE, st 



FIGURE 10.— Grade-tonnage curve, Willow Creek District. 



15 



DISCUSSION 



The remaining gold endowment tables 
presented for the eight districts in- 
dicate the dependence of the estimate on 
the limiting grade chosen. The conserva- 
tive approach based on past mining grades 
was used to determine a likely estimate 
of the nonproduced portion of the endow- 
ment. Based on past production history, 
the estimates listed in the tables can be 
considered to be a conservative estimate 
of remaining gold endowment. Table 11 
presents a summary of the remaining en- 
dowment by district, ranked according to 
quantity remaining. 

The feasibility of mining a deposit in 
any of these districts is not addressed. 
Economic feasibility depends on metal 
prices, deposit characteristics, and re- 
serves and grade. The estimates pre- 
sented above are intended to show the 
possible amount of lode gold remaining. 

Clearly other districts with major past 
producers may have remaining gold re- 
sources and future production potential. 
Not all districts were examined owing to 
the nature of the production data avail- 
able. Exclusion of a district from this 
study does not mean it has limited or no 
potential remaining gold resource. 

The Juneau District has the largest re- 
maining lode gold endowment, at a grade 
of 0.02 tr oz/st. Recent interest has 
been shown in the Alaska Juneau Mine and 



the Treadwell group mines. Barrick Re- 
sources Corp. obtained a lease on certain 
properties in 1984 and has been examining 
mine records and maps. Some fieldwork 
has also been conducted, and exploration 
targets have been defined (10). 

The Fairbanks District has been the 
site of extensive reexamination of past 
producers In recent years. Underground 
work and drilling have taken place at a 
number of properties (10). Presently, 
Silverado Mines LTD, in a joint venture 
with two other participants, is preparing 
to return the Grant Mine to production. 

The Chichagof and Willow Creek Dis- 
tricts have also had recent exploration 
activity, with a focus on reopening past 
producing mines. Interest has also been 
expressed in the other districts that 
were examined. 

It is possible that some of the past 
producing gold mines in Alaska will come 
Into production within the decade. Based 
on the results of this study, more than 
8.4 million tr oz of gold could be pro- 
duced from the eight districts examined, 
provided that the political and economic 
climate is favorable. Other districts 
such as the Alaska Peninsula, Kantishna, 
and Bonnifield also have potential for 
future lode gold production, but lacked 
sufficient production data to be analyzed 
in this study. 



TABLE 11. - Summary of remaining endowment 



District 



Limiting 

grade, 
tr oz/st 



Initial 
ore, st 



Past 
production, 
tr oz gold 



Remaining 
endowment , 
tr oz gold 



Juneau 

Fairbanks , 

Chicagof , 

Willow Creek , 

Hope-Seward , 

Prince William Sound. 

Ketchikan , 

Homer , 

Total , 



0.02 
.7 
.4 
.8 
.4 
.4 
.2 
.8 



385,683,100 

1,229,700 

1,521,200 

909,100 

260,000 

185,300 

79,800 

15,300 



5,583,121 

230,499 

787,347 

607,726 

17,587 

82,777 

16,042 

10,391 



6,758,700 
827,000 
326,200 
316,800 
118,900 
53,000 
9,300 
5,200 



389,883,500 



7,335,490 



8,415,100 



16 



REFERENCES 



1. Musgrove, P. A. Lead: Grade-Ton- 
nage Relation. Min. Mag., v. 112, No. 4, 
1965, pp. 249-151. 

2. Singer, D. A. , D. P. Cox, and 
L. J. Drew. Grade and Tonnage Re- 
lationships Among Copper Deposits. 
U.S. Geol. Surv. Prof. Paper 907-A, 
1975, pp. Al-All. 

3. Ellis, J. R., D. P. Harris, and 
N. H. Van Wie. A Subjective Probability 
Appraisal of Uranium Resources in the 
State of New Mexico. U.S. Energy Res. 
and Dev. Admin. (now part of Dep. En- 
ergy), Open File Rep. GJO-110(76), 1975, 
103 pp. 

4. Lasky, S. G. 
Grade Relations Help 
erves. Eng. and Min. 
1950, pp. 81-85. 

5. . Mineral Resource Appraisal 

by the US Geological Survey. Q. CO Sch. 
Mines, v. 45, No. 1A, 1950, pp. 1-27. 

6. Cargill, S. M. , D. H. Root, and 
E. H. Bailey. Estimating Usable Re- 
sources From Historical Industry Data. 



How Tonnage and 

Predict Ore Res- 

J. , v. 151, No. 4, 



Econ. Geol. and Bull. Soc. Econ. Geol. , 
v. 76, No. 5, 1981, pp. 1081-1095. 

7. . Resource Estimation from 

Mercury, a Test Case. 
Geol. , v. 12, No. 5, 



Mineral Resources 
Univ. Press, 1984, 



Historical Data: 

J. Int. Assoc. Math. 

1980, pp. 489-522. 

8. Harris, D. P. 
Appraisal. Oxford 
445 pp. 

9. Ransome, A. L. , and W. H. Kerns. 
Names and Definitions of Regions, Dis- 
tricts, and Subdistricts in Alaska. Bu- 
Mines IC 7679, 1954, 91 pp. 

10. Eakins, G. R. , T. K. Bundtzen, 
L. L. Lueck, C. B. Green, J. L. Gal- 
lagher, and M. S. Robinson. Alaska's 
Mineral Industry 1984. AK Div. Geol. 
and Geophys. Surv. Spec. Rep 38, 
1985, 57 pp. 

11. Jansons, U. , R. B. Hoekzema, J. M. 
Kurtak, and S. A. Fechner. Mineral Oc- 
currences in the Chugach National 
Forest, Southcentral Alaska. BuMines MLA 
5-84, 1984, 218 pp. 



APPENDIX A.— RAW PRODUCTION DATA FOR DISTRICTS ANALYZED 



17 



TABLE A-l. - Raw production data, Chichagof District 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



1906. 
1907. 
1908. 
1909. 
1910. 
1911. 
1912. 
1913. 
1915. 
1916. 
1917. 
1918. 
1919. 
1920. 
1921. 
1922. 
1923. 
1924. 
1925. 
1926. 
1927. 



60 

1,353 

2,071 

744 

4,282 

10,577 

22,915 

22,000 

33,850 

36,822 

38,794 

33,978 

42,187 

33,243 

33,855 

39,307 

11,639 

44,283 

66,470 

33,725 

8,827 



351 

3,172 

2,792 

992 

7,784 

7,062 

11,447 

11,367 

44,517 

39,453 

39,554 

60,200 

89,097 

83,080 

71,339 

48,707 

26,135 

18,489 

22,609 

25,779 

11,773 



5.85 

2.34 

1.35 

1.33 

1.82 

.67 

.50 

.52 

1.32 

1.07 

1.02 

1.77 

2.11 

2.50 

2.11 

1.24 

2.25 

.42 

.34 

.76 

1.33 



1928. 
1929. 
1930. 
1931. 
1932. 
1933. 
1934. 
1035. 
1936. 
1937. 
1938. 
1939. 
1940. 
1941. 
1942. 
1943. 
1944. 
1947. 
1950, 
1951. 



3,539 

4,071 

1,760 

12,584 

34,333 

15,216 

28,370 

24,500 

21,475 

21,855 

25,588 

23,484 

38,070 

45,919 

4,184 

534 

200 

12 

537 

100 



4,290 

3,818 

490 

6,249 

17,897 

10,912 

9,583 

14,744 

11,866 

15,172 

21,811 

15,267 

12,945 

10,167 

5,081 

776 

22 

11 

397 

151 



1.21 
.94 
.28 
.50 
.52 
.72 
.34 
.60 
.55 
.69 
.85 
.65 
.34 
.22 

1.21 

1.45 
.11 
.92 
.74 

1.51 



10 



TABLE A-2. - Raw production data, Fairbanks District 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



1910, 
1911, 
1912, 
1913, 
1914, 
1915, 
1916, 
1917, 
1918, 
1919, 
1920. 
1921. 
1922. 
1923. 
1924. 
1925. 
1926. 
1927. 
1928. 
1929. 
1930. 
1931. 
1932. 
1933. 
1934. 
1935. 
1936. 
1937. 



148 

875 

4,708 

12,237 

6,526 

6,545 

1,111 

1,200 

1,035 

1,384 

504 

949 

1,524 

1,278 

4,528 

3,663 

1,089 

1,919 

4,871 

4,657 

1,964 

3,222 

12,549 

214 

297 

4,519 

12,418 

14,839 



841 

3,103 

9,417 

16,905 

10,905 

10,535 

1,905 

2,142 

1,294 

1,507 

967 

2,104 

2,542 

1,197 

4,870 

4,064 

788 

4,064 

4,004 

3,618 

2,527 

6,000 

12,590 

222 

389 

3,665 

5,669 

15,688 



5.68 

3.55 

2.00 

1.38 

1.67 

1.61 

1.71 

1.79 

1.25 

1.09 

1.92 

2.22 

1.67 

.94 

1.08 

1.11 

.72 

2.12 

.82 

.78 

1.29 

1.86 

1.00 

1.04 

1.31 

.81 

.46 

1.06 



1938, 
1939, 
1940, 
1941. 
1942, 
1943, 
1944, 
1945, 
1946, 
1947, 
1948, 
1949, 
1950, 
1952. 
1953, 
1954. 
1955. 
1956, 
1957. 
1958, 
1959, 
1960, 
1961. 
1962. 
1963. 
1964. 
1965. 



12,440 

15,474 

17,414 

13,571 

7,054 

3,000 

1,250 

2,427 

1,295 

461 

498 

463 

199 

152 

275 

194 

1 

1 

55 

5 

214 

1,075 

135 

162 

861 

2,447 

3,172 



10,315 

18,117 

18,195 

13,751 

13,502 

3,561 

1,428 

4,217 

1,676 

1,126 

277 

207 

309 

236 

398 

144 

1 

1 

28 

2 

538 

1,215 

279 

293 

1,134 

2,055 

3,556 



0.83 
1.17 
1.04 
1.01 



91 

,19 
,14 
,74 



1.29 

2.44 

.56 

.45 

1.55 

1.55 

1.45 

.74 

1.00 

1.00 

.51 

.40 

2.51 

1.13 

2.07 

1.81 

1.32 

.84 

1.12 



TABLE A-3. - Raw production data, Homer District 



Year 


Ore, 
st 


Gold, 
tr oz 


Grade, 
tr oz/st 


Year 


Ore, 
st 


Gold, 
tr oz 


Grade, 
tr oz/st 


1917 


5 

1 

40 

637 

764 

1,602 

165 

200 

325 

847 


1 



43 

949 

1,121 

2,100 

279 

311 

451 

803 


0.12 
.32 
1.08 
1.49 
1.47 
1.31 
1.69 
1.56 
1.39 
.95 


1932 


21 
423 
326 
255 
1,550 
1,141 
341 

84 
160 

60 


102 

429 

252 

147 

1,497 

1,266 

306 

23 

103 

55 


4.84 


1918 


1933 


1.02 


1924 


1934 


.77 


1925 


1935 


.58 


1926 


1936 


.97 


1927 


1937 


1.11 


1928 


1938 


.90 


1929 


1940 


.27 


1930 


1941 


.64 




1942 


.92 



TABLE A-4. - Raw production data, Hope-Seward District 



19 



Year 


Ore, 

St 


Gold, 
tr oz 


Grade, 
tr oz/st 


Year 


Ore, 

St 


Gold, 
tr oz 


Grade, 
tr oz/st 


1911 


274 

534 

1,133 

1,831 

815 

711 

140 

297 

96 

55 

150 

300 

250 

800 

392 

315 

5 

450 

751 

605 


478 
697 
856 
1,195 
804 
835 
223 
460 
435 
169 
345 
643 
218 
761 
116 
231 
7 
231 
505 
329 


1.74 

1.30 

.76 

.65 

.99 

1.17 

1.59 

1.55 

4.53 

3.08 

2.30 

2.14 

.87 

.95 

.29 

.73 

1.40 

.51 

.67 

.54 


1931 


937 
212 
208 
125 
922 
542 
1,598 
722 
387 

40 
450 
399 
655 
224 
120 

55 
520 

47 
194 

10 


415 

29 

295 

183 

1,208 
707 

1,718 

634 

438 

41 

228 

191 

308 

143 

127 

34 

209 

318 

815 

9 


0.44 


1912 


1935 


.14 


1913 


1936 


1.42 


1914 


1937 


1.46 


1915 


1938 


1.31 


1916 


1939 


1.30 


1917 


1940 


1.08 


1918 


1941 


.88 


1919 


1942 


1.13 


1920 


1944 


1.03 


1921 


1945 


.51 


1922 


1946 


.48 


1923 


1947 


.47 


1924 


1948 


.64 


1925 


1949 


1.06 


1926 


1950 


.62 


1927 


1954 


.40 


1928 


1955 


6.77 


1929 


1956 


4.20 






.90 



20 



TABLE A-5. - Raw production data, Juneau District 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



1891... 
1892. .. 
1893... 
1895... 
1896... 
1897... 
1905... 
1906... 
1907... 
1908... 
1909... 
1910... 
1911. .. 
1912. .. 
1913... 
1914... 
1915... 
1916. .. 
1917... 
1918... 
1919... 
1920... 
1921... 
1922... 
1923... 
1924... 



330 

291 

336 

440 

401 

562 

4 

1,406 

1,210 

1,473 

1,480 

1,429 

1,564 

1,714 

1,567 

1,685 

2,955 

3,481 

3,360 

2,054 

3,211 

3,375 

2,854 

2,463 

2,476 

3,068 



,471 
,865 
,560 
,342 
,765 
,342 
,125 
,746 
,486 
,345 
,871 
,072 
,741 
,336 
,746 
,696 
,339 
,259 
,614 
,676 
,261 
,704 
,076 
,231 
,242 
,217 



37,043 

32,715 

37,725 

50,554 

47,868 

57,774 

3,553 

159,557 

129,953 

159,099 

196,234 

173,116 

180,868 

202,293 

190,485 

185,047 

214,035 

221,177 

165,313 

92,172 

112,706 

127,382 

104,232 

76,088 

69,035 

92,500 



0.11 
.11 
.11 
.11 
.12 
.10 
.86 
.11 
.11 
.11 
.13 
.12 
.12 
.12 
.12 
.11 
.07 
.06 
.05 
.04 
.04 
.04 
.04 
.03 
.03 
.03 



1925... 
1926... 
1927... 
1928... 
1929... 
1930... 
1931... 
1932... 
1933... 
1934... 
1935... 
1936... 
1937... 
1938... 
1939... 
1940... 
1941... 
1942... 
1943... 
1944... 
1945... 
1947... 
1948... 
1949... 
1950... 
1951... 



3,485,976 

3,829,783 

4,267,810 

3,720,087 

3,838,660 

3,924,460 

4,162,350 

4,001,630 

4,428,564 

3,756,206 

3,489,492 

4,366,801 

4,442,765 

4,663,950 

4,648,154 

4,739,792 

4,354,857 

2,765,885 

1,461,905 

379,350 

888 

10 

72 

101 

119 

15 



98,985 

93,913 

112,646 

151,951 

164,477 

162,800 

179,785 

151,347 

151,150 

128,602 

119,032 

149,207 

151,773 

148,015 

128,863 

123,415 

119,618 

77,126 

39,949 

10,316 

734 

8 

102 

391 

352 

41 



0.03 
.02 
.26 
.04 
.04 
.04 
.04 
.04 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.83 
.80 
1.42 
3.87 
2.96 
2.73 



21 



TABLE A-6. - Raw production data, Kechikan District 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



1906 
1907 
1908 
1909 
1910 
1913 
1914, 
1915, 
1916, 
1917, 
1918, 
1919, 
1920, 
1921, 
1922, 
1923. 
1924. 
1925. 
1926. 
1927. 
1928. 



1,650 
200 
100 

2,700 
400 

4,401 

2,250 
626 
800 
716 

1,147 
400 
250 

1,800 
4 

1,350 

7 

90 

15 

2,064 
359 



994 

97 

83 

155 

77 

1,501 

932 

412 

278 

272 

393 

130 

74 

576 

1 

176 

46 

98 

40 

1,406 

544 



0.60 
.48 
.83 
.06 
.19 
.34 
.41 
.66 
.35 
.38 
.34 
.33 
.29 
.32 
.13 
.13 
6.59 
1.09 
2.68 
.68 
1.52 



1929. 
1930. 
1931. 
1932. 
1933. 
1934. 
1935. 
1936. 
1937. 
1938. 
1939. 
1940. 
1941. 
1942. 
1945. 
1946. 
1947. 
1948. 
1949. 
1950. 
1954. 



35 

250 

40 

100 

2,648 

3,012 

3,203 

561 

961 

1,374 

1,415 

1,569 

346 

188 

7 

72 

148 

153 

632 

130 

2 



128 

55 

45 

82 

431 

278 

337 

517 

1,403 

1,414 

914 

1,001 

213 

133 

16 

57 

84 

235 

338 

75 

2 



3.66 
.22 

1.13 
.82 
.16 
.09 
.11 
.92 

1.46 

1.03 
.65 
.64 
.62 
.71 

2.29 
.79 
.57 

1.54 
.53 
.58 

1.00 



22 



TABLE A-7. - Raw production data, Prince William Sound District 



Year 







re, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



1910, 
1911, 
1912, 
1913, 
1914, 
1915, 
1916, 
1917, 
1918, 
1919, 
1920, 
1921. 
1922. 
1923. 
1924. 
1925. 
1929. 
1930. 
1931. 



,440 

,325 

,692 

,650 

,120 

,790 

,513 

,350 

444 

15 

20 

39 

170 

7 

78 

53 

24 

268 

60 



10,745 

7,981 

11,369 

8,229 

7,809 

11,252 

7,739 

4,503 

638 

52 

6 

65 

423 

14 

405 

129 

20 

250 

60 



2.42 

2.40 

2.42 

1.08 

1.10 

.67 

.62 

.84 

1.44 

3.45 

.30 

1.67 

2.49 

1.93 

5.20 

2.43 

.84 

.93 

.99 



1932. 
1933, 
1934. 
1935, 
1936, 
1937, 
1938, 
1939, 
1940, 
1941. 
1942. 
1944. 
1946, 
1948, 
1949, 
1955. 
1963. 
1964. 



52 

95 

1,641 

658 

375 

1,748 

785 

72 

1,204 

3,253 

1,300 

40 

500 

2 

1 

25 

8 

1 



36 

62 

976 

384 

624 

1,014 

1,038 

58 

874 

3,885 

1,775 

17 

282 

291 

4 

26 

3 

1 



0.70 

.65 

.59 

.58 

1.66 

.58 

1.32 

.81 

.73 

1.19 

1.37 

.43 

.56 

4.50 

4.00 

1.04 

.38 

1.00 



TABLE A-8. - Raw production data, Willow Creek District 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



Year 



Ore, 
st 



Gold, 
tr oz 



Grade, 
tr oz/st 



1909 
1010, 
1911, 
1912, 
1913, 
1914, 
1915, 
1916, 
1917, 
1918, 
1919, 
1920, 
1921, 
1922, 
1923, 
1924, 
1925, 
1926, 
1927, 
1928, 
1929, 
1930, 
1931, 
1932, 
1933. 
1934, 



912 

144 

1,048 

3,000 

3,028 

10,110 
6,717 

12,182 
7,883 
7,886 
6,730 
2,850 
3,591 
7,242 
9,132 
8,075 

15,834 

2,537 

7,866 

3,443 

39 

13,975 
7,951 

13,618 

16,578 

17,833 



665 

1,046 

2,596 

4,838 

4,884 

14,376 

11,962 

14,473 

9,466 

12,874 

7,882 

3,067 

5,722 

11,513 

8,622 

9,766 

21,990 

2,082 

7,084 

4,623 

363 

1,725 

21,282 

34,371 

36,867 

38,141 



0.73 
7.27 
2.48 
1.61 
1.61 
1.42 
1.78 
1.19 
1.20 
1.63 
1.17 
1.08 
1.59 
1.59 

.94 
1.21 
1.39 

.82 

.90 
1.34 
9.31 

.12 
2.68 
2.52 
2.22 
2.14 



1935, 
1936, 
1937, 
1938, 
1939, 
1940, 
1941, 
1942, 
1943, 
1944, 
1945, 
1946. 
1947, 
1948, 
1949, 
1950, 
1951. 
1952. 
1953. 
1954. 
1955. 
1958. 
1960. 
1961. 
1963. 



18,332 

27,550 

50,399 

22,965 

45,302 

62,740 

50,240 

32,389 

16,280 

600 

1,967 

2,698 

562 

355 

5,416 

10,270 

410 

205 

200 

240 

56 

31 

136 

72 

5 



16,501 

17,815 

37,467 

31,804 

38,958 

51,490 

48,194 

37,549 

13,079 

3,839 

1,838 

1,275 

358 

476 

5,071 

8,806 

335 

70 

46 

156 

39 

46 

132 

97 

3 



0.90 
.65 
.74 

1.38 
.86 
.82 
.96 

1.16 
.80 

6.40 
.93 
.47 
.64 

1.34 
.94 
.86 
.82 
.34 
.23 
.65 
.70 

1.48 
.97 

1.35 
.60 



23 



APPENDIX B. --REGRESSION ANALYSIS RESULTS, BY DISTRICT 

CHICHAGOF DISTRICT 
Equation coefficients: 
bO = 2.6669 bl = -0.4533 

Partitioned sum of squares 

Source of variation Degrees of Sum c~. squares 

freedom 

Due to regression 1 0. 1 101 

Deviations from regression 7 0.0OO1 

Total 3 0.1 102 

F = 5,529.26 

Coefficient of determination (r squared) = 0.9987 
Correlation coefficient (r) = 0.9994 



FAIRBANKS DISTRICT 
Equation coefficients: 
DO = 1.0672 bl = -0. i860 

Partitioned sum of squares 

Source of variation Degrees of Sum of square; 

f r eedom 

Due to regression 1 0. 0200 

Deviations from regression 8 0.0002 

Total 9 0. 0203 

F = 655.84 

Coefficient of determination (r squared) = 0.9879 
Correlation coefficient (r ) = 0.9940 



25087 241 



24 



HOMER DISTRICT 
Equation coefficients: 
bO = 0.9072 bl = -0.2149 

Partitioned sum of squares 

Source of variation Degrees of Sum of square? 

♦ reedom 

Due to r egression 1 0. 00 19 

Deviations from regression 1 0.0000 

Tota 1 2 0. 00 19 

F = 998. lt> 

Coefficient of determination '.r squarec) = 0.9990 
Correlation coefficient ir ) = 0.9995 



H0PE-SEWARD DISTRICT 
Equation coefficients: 
bO = 1.0100 bl = -0.23S2 

Partitioned sum of squares 

Source of variation Degrees of Sum of square-; 

freedom 

Due to regression 1 0.0408 

Deviations from regression 5 0.0003 

Total 6 0.04H 

F = 600.84 

Coefficient of determination (r squared) = 0.9917 
Correlation coefficient (r) = 0.9959 



25 



JUNEAU DISTRICT 
Equation coefficients: 
bO = 2.1353 bl = -0.4282 

Partitioned sum of squares 

Source of variation Degrees of Sum a* squares 

f reeaom 

DLis to regression 1 0. I2&& 

Deviations from regression 6 0.0OO2 

Total 7 0.1270 

F = 3,270.77 

Coefficient of determination (r squared) = 0.99S2 
Correlation coefficient (r) = 0.9991 



KETCHIKAN DISTRICT 
Equation coefficients: 
bO = 1.30S0 bl = -0.3686 

Partitioned sum of squares 

Source of variation Degrees of Sum of squares 

freedom 

Due to regression 1 0. 0640 

Deviations from regression 4 0.0001 

Total 5 0.0641 

F = 5,042.70 

Coefficient of determination (r squared) = 0.9992 
Correlation coefficient (r) = 0.9996 



26 



PRINCE WILL I Mil SOUND DISTRICT 
Equation coefficients: 
bO = 2.2594 bl = -u.4545 

Partitioned sum of squares 

Source of variation Degrees of Sum of square? 

f reedom 

Due to rsgressi on 1 0. 04 76 

Deviations from regression 5 0.0001 

Total 6 0.0478 

f = 1,611.45 

Coefficient of determination (r squared) = 0.9969 
Correlation coefficient (r ) = 0.99S5 



WILLOW CREEK DISTRICT 
Equation coefficients: 
bO = 1.2777 bl = -0.2132 

Partitioned sum of squares 

Source of variation Degrees of Sum of square? 

freedom 

Due to regression 1 0.0609 

Deviations from regression S 0.0004 

Total 9 0.0613 

F = 1, 144.77 

Coefficient of determination (r squared) = 0.9931 
Correlation coefficient (r) = 0.9965 



U.S. GOVERNMENT PRINTING OFFICE: 1987 -605-017/60040 ! go INT.-BU.OF Ml NES,PGH. , PA . 28465 



U.S. Department of the Interior 
Bureau of Mines— Prod, end Distr. 
Cochrans Mill Road 
P Box 18070 
Pittsburgh. Pa. 15236 



OFFICIAL BUSINESS 
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